Particularly in high-end passenger vehicles, it is increasingly customary in the automotive industry to offer vehicle seats that are covered with genuine leather. To that end, it is known to use leather that supports a layer of soft foam laminated to its inside or back side, which foam improves its cushioning properties and increases seat comfort. As a rule, the foam is a soft polyurethane (PUR) foam, which is ether-based as well as ester-based. Because of the sticky or clinging properties of the soft foam surface, leather having its back side laminated solely with soft foam cannot easily be handled by conventional sewing machines. For this reason, the outside of the soft foam layer is provided with a laminated textile fabric that increases the slipperiness properties of the back side of the leather composite material thus produced so that it can be handled more easily. At the same time, this slipperiness is also important for a seat covering because it allows the seat covering to slide to the required extent in relation to the padding when an elastic deformation occurs during use.
In practice, the above-described leather composite material for seat covers is frequently manufactured by flame-treating one side of a PUR soft foam layer in order to melt the foam and then embedding a textile cloth in the heat-liquefied foam. The disadvantage to this process is that it involves the burning of PUR foam, which gives off noxious emissions. In addition, foam that has been treated with a so-called flame coating of this kind has a tendency to give off pollutants, also referred to as “fogging,” which means that it gives off a certain annoying odor.
Aside from this, using the known leather composite material with a textile backing on the outside of the soft foam layer has a fundamental problem in that the textile material that is laminated to the outside of the foam layer has a different elongation, or stretching properties, than the leather layer of the composite material. The textiles currently on the market that are used for the lamination do not have the elongation coefficients in the longitudinal and lateral direction required by currently used seat shapes and types of leather used for them. If the textile material layer in the composite material has a lower elongation than the leather, then the leather gathers when the leather-covered composite material is rolled toward the leather side or is even merely deformed. In an automobile seat, this gathering appears in the form of wrinkles in the leather surface. Because the textile cloth backing on the outside of the PUR soft foam layer was indispensable in order to produce the slipperiness required in order to be able to use the composite material, it has been necessary to accept the accompanying problems of wrinkle formation in the leather when it is stretched or deformed.